1. Field of the Invention
This invention relates to a method for connecting display panel substrates, and to a device for implementing same.
2. Description of Related Art
A display panel is fabricated by connecting together two substrates. A conventionally used substrate connecting process is now described with reference to FIG. 11. As illustrated in this diagram, a first substrate 110 is held on a first surface table (also known as “upper surface table”) 142 provided with an X-axis driving mechanism 132. Similarly, a second substrate 112 provided with a sealant is held on a second surface table (also known as “lower surface table”) 144 provided with a Y axis driving mechanism 134. Whilst observing alignment marks provided on the first substrate 110 and the second substrate 112, the X axis, Y axis are adjusted, along with a θ axis by means of a θ table 162 position beneath the second surface table 144. In other words, the second substrate 112 is aligned in position with the first substrate by rotating it in a horizontal plane by means of a rotating driving mechanism 136. Thereupon, the substrates are pressurized and connected by means of vertical raising and lowering means 138 and a pressure cylinder 160 capable of moving the first surface table 142 or second surface table 144 in the direction of arrow A. Since the gap between the two substrates (hereinafter, called “cell gap”) is not uniform, display irregularities occur. Therefore, in order to maintain display quality, it is necessary to maintain an appropriate cell gap. This technology is called “Cell Gap Control”. A substrate pressurizing mechanism comprising the aforementioned X axis driving mechanism 132, Y axis driving mechanism 134, rotation driving mechanism 136, vertical raising and lowering means 138, and pressure cylinder 160 is generally known in the prior art, comprising a variety of mechanisms. Therefore, since a mechanism of this kind can be constructed readily by a specialist in this field, detailed description thereof is omitted here.
For example, the connecting process in the fabrication of liquid crystal display elements using glass substrates, or the like, is performed by inserting a spacer made from glass fibre, or the like, together with the sealant, whilst simultaneously scattering a spacer made from resin, silica, or the like, over the entire interior surface of the cell between the substrates. However, this involves a detrimental effect in that the spacers reduce the contrast, and the like. In order to improve display quality, a so-called “spacer-less” liquid crystal display is anticipated, wherein precise cell gap control can be achieved without placing spacers inside the cells.
Moreover, in organic EL panels, and the like, which have been the subject of increasing demand in recent years, it is not possible to place spacers on the entire interior surface of the cells, and hence precise cell gap control has not been achieved.
Furthermore, in the case of a liquid crystal display element using glass substrates, or the like, in order to sealing the interior of the cell completely, it is necessary to implement a process for initially placing the sealant, following by a process for sealing the opening section used to introduce the liquid crystal medium by providing sealant on that opening section, and therefore it has not been possible to provide sealant in such a manner that the interior of the cell is sealed completely in a single process. Consequently, the process for sealing the opening section is appended after the introduction of the liquid crystal medium, and therefore it is difficult to guarantee the adhesive strength of the sealed section, thereby giving rise to problems such as leaking of the liquid crystal medium after sealing, or the like.
Furthermore, in the case of an organic EL panel, since it is necessary to expel the air inside the cell when connecting the substrates, in many cases, rather than sealing the panel completely with the sealant, a process is adopted whereby a small gap is left in a portion of the panel and this gap is sealed at the same time that the substrates are pressurized and the cell gap is determined. However, problems frequently occur with respect to the adhesive strength of the sealing of this gap, and as a consequence, the display quality of the panel is degraded, and product lifespan is shortened.